JPH0527967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a dry etching apparatus for etching a substrate using plasma discharge.

(Prior Art) As this type of apparatus, a parallel plate type dry etching apparatus has been conventionally known.

This parallel plate type dry etching device has a fourth
As shown in Figure a, a cathode electrode 2 is placed inside the vacuum chamber 1.
and an anode electrode 3 are opposed to each other, while a high frequency power source 4 is connected to the cathode electrode 2, and a substrate 5 is placed directly on the cathode electrode 2.

When a predetermined gas is introduced into the vacuum chamber 1 and high frequency power is applied to the cathode electrode 2,
Plasma is generated between both electrodes 2 and 3.

When plasma is generated in this way, as shown in FIG. 4b, the plasma potential voltage Vp and
A potential difference occurs with the self-bias voltage Vs of the cathode electrode 2, and the ions are accelerated by this potential drop (Vp-Vs) and irradiate the substrate 5. Therefore, the greater the potential difference, in other words, the greater the absolute value of the self-bias voltage Vs, the greater the ion irradiation energy to the substrate 5.

By increasing the ion energy in this way,
Etching with strong anisotropy becomes possible and the processing accuracy improves, but if the high frequency power is increased for this purpose, the ion energy will become too large and the substrate 5 may be damaged. Ta.

Particularly, during over-etching, in which details are etched after the etching process has been completed, the damage caused by the ion bombardment becomes large, and the device characteristics of the substrate 5 are sometimes impaired.

(Problems to be Solved by the Invention) In order to reduce the above-mentioned ion bombardment, conventional methods have been to increase the pressure inside the vacuum chamber 1 or reduce the self-bias voltage Vs by reducing the high-frequency power. Ta.

However, if the pressure inside the vacuum chamber 1 is increased or the high-frequency power is decreased, plasma generation becomes unstable, and sufficient ion energy cannot be obtained during etching other than over-etching, resulting in the anisotropy being reduced. As it became weaker, there were problems such as a decrease in processing accuracy.

Additionally, a device described in Japanese Patent Application Laid-Open No. 58-202531 is known as a device for controlling this ion energy, but since this device places a substrate on the anode electrode, Only the self-bias voltage Vp can be controlled. for that,
As shown in FIG. 4b, the voltage control range becomes smaller. Therefore, this conventional device has a problem in that the control range of ion energy must also be narrowed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dry etching apparatus that causes less ion bombardment on the substrate during over-etching while maintaining highly anisotropic etching characteristics.

(Means for Solving the Problems) This invention includes a cathode electrode to which high-frequency power is applied in a vacuum chamber, and an anode electrode insulated from the grounded vacuum chamber, and a substrate is placed on the cathode electrode. However, a tuned circuit with variable conductance and capacitance is connected to the anode electrode.

(Operation of the present invention) With the above configuration, the phase of the voltages of both electrodes can be arbitrarily adjusted by adjusting the conductance, capacitance, etc. of the tuned circuit.

When the phase is shifted by 180 degrees, the self-bias voltage becomes maximum, and when the phase difference is made zero, the self-bias voltage becomes minimum.

(Effects of the Present Invention) According to the device of the present invention, the self-bias voltage can be arbitrarily adjusted even when the high-frequency power is constant, so that the optimal self-bias voltage can be selected depending on the conditions of use.

Therefore, while using the minimum high-frequency power necessary to generate stable plasma, the self-bias voltage is increased during normal etching.
It has strong anisotropy and can maintain etching characteristics with high processing accuracy. Furthermore, during over-etching, the self-bias voltage can be lowered to reduce ion bombardment, thereby solving the problem of damage to the substrate.

Also, since the substrate is placed on the cathode electrode,
Since the potential voltage and the self-bias voltage can be controlled simultaneously, the control range can be kept sufficiently large.

(Embodiment of the present invention) The first embodiment shown in FIG. It is insulated from the vacuum chamber 11.

The cathode electrode 12 has a high frequency matching circuit 16
The anode electrode 13 is connected to a high frequency power source 17 through a tuning circuit 18 .

This tuning circuit 18 connects a coil 18a and a capacitor 18b in parallel, and makes their conductance and capacitance variable.

Furthermore, a flow rate regulator 19 is provided in the vacuum chamber 11.
and a gas introduction path 21 having a cut valve 20, and is also connected to a vacuum pump 24 via a cut valve 22 and a pressure regulator 23.

Then, the substrate 25 is placed on the cathode electrode 12, the cut valve 22 is opened, the vacuum pump 24 is driven, and the inside of the vacuum chamber 11 is evacuated. When the inside of the vacuum chamber 11 is sufficiently evacuated in this way, the cut valve 20 is opened and the flow rate regulator 1
A predetermined gas is introduced through 9.

Then, by operating the pressure regulator 23, the vacuum chamber 1
1 to a predetermined pressure, and a high frequency power source 1.
7 is operated to apply high frequency power to the cathode electrode 12 via the high frequency matching circuit 16.

When high-frequency power is applied to the cathode electrode 12 in this manner, a plasma discharge is generated within the vacuum chamber 11, so that a potential difference is generated between the plasma potential voltage Vp and the self-bias voltage Vs of the cathode electrode 12. And this potential drop (Vp−Vs)
Since the ions are accelerated and irradiate the substrate 25,
The substrate 25 is etched.

At this time, by adjusting the conductance of the coil 18a of the tuned circuit 18 connected to the anode electrode 13 and the capacitance of the capacitor 18b, the phase of the anode electrode 13 side with respect to the high frequency power connected to the cathode electrode 12 is adjusted. can be shifted.

Then, by shifting this phase by 180 degrees, both electrodes 1
Since the potential difference between 2 and 13, in other words, the potential difference (Vp - Vs) between the potential voltage Vp and the self-bias voltage Vs increases, the self-bias voltage Vs generated on the surface of the electrode 12 also becomes relatively high. . As the self-bias voltage Vs increases in this way, the ion bombardment also increases, so that highly anisotropic etching is possible and the processing accuracy is also improved.

Also, when the phase difference is set to zero, the potential difference (Vp−
Vs) becomes smaller, so the self-bias voltage Vs
becomes relatively low, and the impact force of the ions also becomes smaller accordingly.

Even if the high frequency power is constant in this way, the self-bias voltage Vs on the cathode electrode 12 side can be controlled by adjusting the above-mentioned phase. , above self-bias voltage Vs
It is also possible to maximize.

In other words, while using the minimum high-frequency power, the self-bias voltage Vs can be maximized to increase ion bombardment and process with strong anisotropy. During over-etching, the above-mentioned phase difference can be set to zero and the self-bias voltage can be increased. can be lowered to reduce ion bombardment.

Note that controlling the self-bias voltage Vs by shifting the phase of the anode electrode 13 with respect to the high-frequency power applied to the cathode electrode 12 means that
The principle is the same as controlling the self-bias voltage Vs by controlling the discharge impedance between the electrodes 12 and 13. In other words, if the discharge impedance is decreased, the self-bias voltage will be decreased, and if the discharge impedance is increased, the self-bias voltage will be increased.

In the second embodiment shown in FIG. 2, solenoid coils 26 and 27 are provided outside the vacuum chamber 11, and an insulator 28 is provided in addition to the insulator 14 on the cathode electrode 12 side. The portion of the electrode 12 other than the plasma irradiation surface is hidden.

The configuration other than the above is the same as that of the first embodiment.

When DC power is applied to the solenoid coils 26 and 27, a magnetic field in the direction of the arrow 29 is generated, and therefore the electrons undergo pseudo-cycloid motion under the influence of the magnetic field.

When the electrons make pseudo-cycloid motion in this way, the plasma becomes even more dense, so the discharge impedance can be reduced accordingly.

By reducing the discharge impedance in this manner, the self-bias voltage Vs generated on the cathode electrode 12 side can be reduced, so that damage to the substrate 25 due to ion bombardment can be eliminated.

Note that the magnetic field generated between both electrodes 12 and 13 may be not only a unidirectional magnetic field as described above, but also an alternating magnetic field or a rotating magnetic field. In particular, an alternating magnetic field or a rotating magnetic field can more easily achieve high plasma density, so the effect is even more pronounced.

The third embodiment shown in FIG.
A pair of magnets 30, 31 and 32, 33 along 3
It is possible to generate plasma with higher density.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the first embodiment, Figure 2 is a schematic diagram of the second embodiment, Figure 3 is a schematic diagram of the third embodiment, Figure 4a is a conventional schematic diagram, Figure 4 b is the plasma potential voltage Vp and self-bias voltage
It is a graph showing the relationship with Vs. 12... Cathode electrode, 13... Anode electrode, 1
8... Tuned circuit.

Claims (1)

[Claims] 1. A vacuum chamber is provided with a cathode electrode to which high-frequency power is applied and an anode electrode insulated from the grounded vacuum chamber, a substrate is placed on the cathode electrode, and a substrate is placed on the anode electrode. , a dry etching device connected to a tuned circuit with variable conductance and capacitance. 2. The dry etching apparatus according to claim 1, further comprising means for generating a magnetic field along the cathode electrode on which the substrate is placed and orthogonal between both electrodes.